Glass composition colored by copper and tin, and method of manufacturing same



Unit Sate GLASS COMPOSITION COLORED BY COPPER AND TIN, AND METHOD OFMANUFACTURING M Thomas B. Parks, Milwaukee; Wis., assignor to .l os.Schlitz Brewing Co., Milwaukee, Wis., a corporation of Wisconsin NoDrawing. Application June 20, 1957 Serial NO; 667,044

6 Claims. (Cl. 106- 52) This present application is acontinuation-in-part of the copending application of the same inventor,for Glass Composition Colored by Copper and Tin and Method ofManufacturing Same, Serial No. 557,141, filed January 3, 1956, and nowabandoned.

This present invention relates to glass composition colored by copperand tin, and method of'manufacturing same. The colored glass of thisinvention is chiefly ruby,'from pink through red to-black, and theinvention more particularly resides in-a composition and a method forits preparation, wherein there is included with the ordinary ingredientsof a silicate-glass-making mix, copper introduced prior to the melt,accompanied by urea, the coloration being assisted by the inclusion oftin.

Copper has long been used as a coloring agent for glass-to develop aruby coloration; but in order to obtain the desired effect in open ortank furnace melting, it has been necessary to use, in conjunctionwiththe copper, cyanogens as reducing agents. Practical commercialproduction of ruby glass, in this fashion, has been carried on, but aserious toxicity problem is, of course, involved. Somehave asserted thatpulverized coal may be substituted for the cyanogen, but if coal beused, difficulties with free carbon, sulfur compounds, and metallicoxides, may be expected; A variety of otherreducing agents are known tobe effective but only when used in conjunction with'closed pot melting.

Full coloration is not developed in either cyanogen or coal'reducedcopper ruby glass'unless thefinished: articles are subjected tostriking. Another difficulty. which has been'encountered withcyanogen'reduced copper. and coal reduced copper, is that it hasbeenxfound'necessary to suppress streaking and lack of uniformity byinclusion of bismuth, and this element may cause a dark surfacehaze,which obscures both the transparency and the color of the glass beneath.

It is an object of this invention to prepare from ordinary'silicate-glass-making materials, in open or tank furnaces, a glasshaving a color'dependent upon the presence of metallic copper.

It is a further object that this glass be free of any appreciablesurface haze due to bismuth.

his a further object that this glass be prepared without resort toground coalas a reducing substance or tothe dangerous and toxiccyanogenleducing. substances.

It is a further object that this glass be able to develop its full colorwith or without. striking. a

Itis a further. object that the process bevery inexpen- 2,922,726Patented Jan. 26, 1960 2 products of urea; (2) a copper compound capableof combining with ingredient No. 1 above; and (3) metallic tin(preferably comminuted) or an appropriate tin' compound.

The following copper compounds are appropriate: cuprous oxide, cupricoxide, and copper acetates, borate, carbonates, chlorides, cyanurate,hydroxides, nitrate, oxalate, phosphates, and sulfates. Mixtures ofappropriate copper compounds may be employed, and suchmixtures are to beconsidered as though a single compound within the scope of the claims.Cuprous oxide is preferable, cupric oxide being a close second.

The following tin compounds are appropriate: stannic oxide, stannousoxide, and tin chlorides, oxalate, and sulfates. Mixtures of appropriatetin compounds, mixed with or without metallic tin, may be employed, andsuch mixtures are to berconsidered as though a single compound- Withinthe'scope of the claims. Stannic oxide is preferable, stannous oxidebeing a close second.

The ingredients of the copper-tin-urea mixture can be added unreacted tothe glass-making mix. Or all three ingredients can be reacted together,then ground, and then added to' the. mix. Or the copper and urea.ingredients can be reacted together, then ground, and then added, thetin ingredients being added unreacted. Accordingly the term urea isusedin the claims as generically including urea, biuret, and otherpyrolytic products'of urea; and'the term adding a copper-tin-ureamixture is used in the. claims as genericallyincluding adding theseveral ingredients of this mixture in any manner to the silicate-glassmix.

The coloration effected by the present invention is due to-thecolloidalsuspension of particles of metallic copper in the glass. On theanalogy of gold ruby glass, it is belielved that below a certain sizethe copper particles produce no color effect; within an optimum range ofsize they produce the ruby colors (the intensity dependingon theconcentration of the copper); and above that range the copper colorcombines with the wave-length-reflectibn effect to produce a liverycoloration.

The exact action. of the tin isnot understood, but the presenceof;smallquantities of a tin compound has been found essential to enablethe copper to produce the desired effect.

The success of present invention is believed to be due to its producingthe right particle-size and distribution of copper particles, evenwithout striking, And although, as already stated, the present inventionis not limited to the order of introduction of the ingredients of thecoppertin-urea mixture, it has been found that the best results areobtainedif the three ingredients are all-reactedtogether. before beingadded. This is believed due to a better particle size and distributionof the metallic. copper in the finished glass, when the copper and ureaare reacted together before being added, and to a better juxtapositionof'the copper particles and the particles of the tin-compound in thefinished glass when all three ingredients are reacted together beforebeing added.

Regardless of what copper compound is. employed, one atomic weight ofcuprous copper will require four molecular weights of urea, or thecorresponding weight of a pyrolytic product of. urea, for example twomolecular weights of biuret. An excess of urea, or its pyrolyticproducts, however, does notaffectj the coloring adversely, unlessupwards of 10' to 12 molecular weights of urea (or corresponding weightsof pyrolytic products of urea) are used for each atomic weight ofcuprous copper. Larger excesses may produce carbon deposits and" aresulting loss-'of-'generaltransparency.

In the case of cupriccopper compounds; the abovementioned figures shouldbe doubled'. 'fi 1 Modified. reds may be obtained by the presence of 3coloring oxides, such as iron, cobalt, nickel, manganese, and the like,in the finished glass, especially in the case of the lighter reds of thelower copper concentrations;

and such modified colors are within the scope of the present invention.4

The present invention may be practiced as follows. It is usual toprepare the copper-tin-urea mixture first in considerable quantity. Asalready stated, this may be performed in various ways.

For example copper biuret, so termed even when the precisestoichiometric ratio of its ingredients is not attained, may be preparedby first heating urea to a temperature of from. 120 to 160 C. orthereabouts to initiate softening, melting and decomposition, duringwhich melting and decomposition ammonia is given off and there is formedmolten biuret. This preliminary heating step is substantially completein approximately fifteen to twenty minutes, and the melt is then readyto receive the addition of an appropriate copper compound, preferably inthe form of a powder. The proper proportions of urea and copper compoundhave already been stated. The powder is added slowly with stirring. Adeep blue copper complex begins to form at once, but the reaction is notcomplete until held for about fifteen to thirty minutes at approximately170 'to 175 C. However it is not essential, although preferable, thatthis additional heating occur at exactly this point, as it may besupplied by later conventional steps of the glassmaking. The meltedcomposition is then poured on a cold surface to chill and solidify itafter which the solidified material may be reduced to a powdermechanically. The tin required in the composition may be added directlyto the copper biuret melt, before the melt is solidified, in the form ofmetallic tin or an appropriate tin compound, as described earlierherein. When the tin is thus added, a tin-copper complex is formed whichmay be termed tin-copper biuret.

The tin ingredient, instead of being added to the copper biuret melt, asabove described, may be later mixed with the ground copper biuret, orwith the other glass-making ingredients.

Or the urea ingredient, the copper ingredient, and the tin ingredientmay be merely mixed into the other glass making ingredients, and thewhole then fused, but such renders difficult the uniform incorporationof thecopper and its eflective reduction. Streaking may ensue and darkand cloudy carbon inclusions may occur from decomposition of excess ureanot accessible to copper because the mixture is not suflicientlyintimate.

The quantity of tin employed should be such as to cause theconcentration of tin, by weight, in the finished glass, in terms ofstannic oxide, to range between A and 3% times the concentration ofcopper in terms of cuprous oxide. Although there appears to be littleadvantage from the color standpoint in tin concentrations in excess ofabout 0.25% in terms of stannic oxide, somewhat higher percentages havelittle disadvantage other than increased cost, which however is aserious consideration. I

But too much tin produces a livery color in the glass. Three andone-half times the concentration of copper is believed to be a safeupper limit.

.As stated earlier herein, the tin can be introduced in the form ofeither metallic tin, or one of certain stannous or stannic compounds.But if a stannic compound be used, a corresponding excess of urea shouldbe introduced to compensate. for that which is oxidized by the stanniccompound.

By introducing, into the glass-making mix, the copper already reactedwith the urea, a sustained reducing eifect carrying through theglass-making operation apparently occurs. This not only producesmetallic copper in the quantity required for coloration but also causesprecipita tion of this copper in a distribution and particle size 4which reaches optimum color levels simultaneously with the completion ofthe glass article. Neither bismuth to moderate and extend theprecipitation of the copper, nor striking to develop the color appear tobe necessary, except where the glass is so worked that reprecipitationof copper becomes advisable, and a glass free of the darkening haze ofbismuth inclusions is produced by a shorter and more economicaloperation.

However, where processing must be prolonged for any reason, or where thesurface condition produced .by bismuth is desirable, bismuth may, attimes, be included to advantage, although its presence is not requiredand is not ordinarily advantageous.

In the practice of the present invention, regardless what copper, tin,and urea ingredients are selected, and whether and how combined or notbefore addition, these ingredients are customarily added to theconventional ingredients of the selected silicate-glass-making mix, andthen thoroughly blended; before being charged into the crucible.

The ratios of the copper, tin, and urea ingredients have already beendiscussed. The total quantity of the copper-tin-urea mixture to beadded, should be such that the concentration of copper in the finishedglass, in terms of cuprous oxide, will fall between 0.03% and 0.25%.0.03% to 0.05% produces a pink coloration; 0.05% to 0.125% produces thelight and brighter ruby reds; 0.125% to 0.25% produces dark reds; above0.25% produces nearly black.

Where the best ruby colors are desired, it will be found desirable toinclude in the initial mix, barium or strontium, either as anappropriate barium or strontium compound. The following are appropriatecompounds: the respective acetate, borate, carbonate, chloride,hydroxide, nitrate, nitrite, oxalate, oxide, peroxide, phosphates,silicate, sulfate, and sulfite. Mixtures of appropriate barium and/ orstrontium compounds may be employed, and such mixtures are to beconsidered as though a single compound within the scope of the claims.Barium is preferred, and the preferred form for its introduction isbarium carbonate. The quantity to be added should, in any case, be suchthat the concentration thereof in the finished glass, in terms of bariumoxide and/ or strontium oxide, falls between 0.1% and 1.0%. Whileclarity, color, and gloss are improved by barium or strontium, theotherphysical properties of the glass appear to be unimpaired.

Inasmuch as barium (introduced in the form of barium carbonate or bariumoxide) is a conventional ingredient of barium silicate glass, inaddition to its particular value in connection with ruby glass, theupper limit of 1.0% does not hold for those two compounds, and may begreatly exceeded without harm. But, if introduced in the form of otherof the earlier listed barium compounds in excess of 1.0%, or in the formof strontium compounds in excess of 1.0%, it is liable to adverselyaffect the development of the ruby color.

Conventional blending, charging, melting, fining, and annealingtechniques may be followed, just as though the copper-tin-urea mixturehad not been added to the mix. Generally no striking step is necessary,but in exceptional circumstances, may be employed to enhance the effect.

The final result is a colored glass consisting of a fusible solidpredominantly comprising silicious and basic oxides, colored bycontaining colloidally suspended precipitated metallic copper derivedfrom the pyrolytic decomposition of copper compounded with urea,assisted by a tin compound, and further assisted by the presence ofbarium or strontium in some form, if employed.

EXAMPLE 1 As a specific instance, a glass composition was made up byweighing up and mixing on a roll mill to thoroughly Q3 blend the same1,044 parts of sand, 94 parts of potassium carbonate, 377 parts ofsodium carbonate, 230 parts of calcium carbonate, 44 parts of borax, and93 parts of nepheline syenite. To this was added and thoroughly blended:2.4 parts of stannic oxide, and 13 parts of copper biuret, prepared asdescribed earlier herein from urea and cuprous oxide.

g The blended mix was then charged at intervals in divided portions intoan open crucible preheated in a gas fired furnace to approximately 1,500C. Charging was at a rate low enough so that temperatures weremaintained above 1,450 C. The fully charged batch was then heated forone hour at 1,500 C. to insure complete melting. The temperature wasthen lowered to 1,450 C. for one hour of preliminary fining. Fining wascompleted by permitting the temperature of the melt to decrease to1,400" C. during a period of approximately one-half hour.

The melt at a temperature between 1,350 and 1,400 C. was then poured onheated glass-rolling apparatus to form a flattened sheet which was thenimmediately transferred to an annealing oven at 450 C. The annealingtemperature was maintained for about thirty minutes and thereafter thesheet was permitted to cool.

The sheet, thus prepared, exhibited a uniform rich ruby coloration, eventhough no striking s'tep had been performed; and had a composition, interms of the oxides, approximately as follows:

Oxide Basis Parts Percent EXAMPLE 2 EXAMPLE 3 When for the stannic oxideemployed in Example 1, there is substituted an equivalent quantity ofcomminuted metallic tin, stannous oxide, or one of the chlorides,oxalate, or sulphates, of tin, comparable results are obtainable.

EXAMPLE 4 When for 23 parts of the sodiumcarbonate employed in Example1, there was substituted 17 parts of barium carbonate, there wasobtained a finished glass of color, finish, and clarity, superior tothat of Example 1.

EXAMPLE 5 When for the barium carbonate of Example 4, there issubstituted an equivalent quantity of one of the acetate, borate,chloride, hydroxide, nitrate, nitrite, oxalate, oxide, peroxide,phosphates, silicate, sulfate, and sulfite, of barium, comparableresults are obtainable.

EXAMPLE 6 When for the barium carbonate of Example 4, there issubstituted an equivalent quantity of one of the acetate, borate,chloride, hydroxide, nitrate, nitrite, oxalate, oxide, peroxide,phosphates, silicate, sulfate, and sulfite, of strontium, satisfactoryresults are obtainable.

Advantages It was the discovery of the invention, shown, described, andclaimed in U.S. Patent No. 2,452,968 to Erwin C.

6 Uihlein and James W. Lawrie that, when beverages, such as-vbeer,containing proteins, are confined in a light-absorbing container whichsubstantially transmits light waves of the order of from about 5,600angstrom units to about 7,000 or 10,000 angstrom units, andsubstantially excludes light waves of below and above those approximatelimits,'there results no damage, and even an inherent improvedstabilization of said contents. Comparable results. may be obtained withother sensitive substances,

notably dairy products, I certain other foods, certain pharmaceuticals,and certain light sensitive chemical compounds.

Ruby glass made in accordance with the present invention, like certainother more expensive copper ruby glasses, is ideal for excludingdeleterious w-ave lengths and for admitting beneficial wave-lengths. Butthe cost of glass of equivalent properties in this regard, as previouslyproduced, has precluded its popular use.

Since the cost of urea is low and the amounts of copper and tinrequired, in accordance with the present invention, to produce asatisfactory color are comparatively small, and since no specialprovisions on account of toxicity are required, and striking in mostcases can be dispensed with, a ruby container glass costing little morethan glass of normal composition may be produced by the method ofthe-present invention. Low cost containers are thus made availablehaving the usual advantages of glass, with the additional advantage thatthere is less deterioration of light-sensitive materials packagedtherein. Specific protection is thus made available on a competitivecost basis feasible for the manufacture of even sooalled nonreturnableor disposable containers.

The following is a brief summary of an extension comparative test of theefiect of light on bottled beer. Five standard brands of beer were eachbottled in five different types of bottle, exposed daily from 8 a.m. to5 p.m., to difiused daylight, supplemented by daylight fluorescentlamps, the light intensity at the bottles varying from 45 tofoot-candles. Control samples were kept in darkness. After four days ofexposure the following was observed. Beer in medium amber non-returnablebottles: characteristic sunstruck odor and taste. Beer in green ale-typebottles, and beer in clear bottles: extreme sunstruck odor and taste.Beer in medium amber export bottles: somewhat sunstruck odor and taste.Beer in ruby bottles: odor normal; taste excellent, even smoother thanthe control. In another experiment, beer exposed to daylight inreturnable and non-returnable ruby bottles for as much as six monthsshowed negligible deterioration.

In addition to its primary use as an inexpensive material ideal 'for themanufacture of containers for the preservation and improvement of beerand other lightsensitive substances, the colored glass of the presentinvention affords an inexpensive and unusually attractive material forvarious aesthetic uses.

In any claim, the mention of any metal is not intended to imply thatthat metal either does or does not exist in metallic form, except wherethe form in which it exists is specifically stated in that connection.

What is claimed is:

l. A process for directly forming a ruby red glass. having colordependent upon the presence of copper, including the steps of adding toa silicate-glass-making batch a complex comprising a copper-tin-biuretincluding as components a copper compound, a tin compound and urea in anapproximate proportion ranging from 4 to 10 molecules or urea for eachatomic weight of cuprous copper, said biuret being in quantities andproportions sufficient to cause the concentration of copper in thefinished glass, in terms of copper oxide, to fall between 0.03% and0.25%, and the concentration of tin, in terms of stannic oxide, to fallbetween A and 3 /2 times the concentrate of copper; and then fusing andfining said batch in an open furnace.

batch independently of the copper compound and urea.

3. The process of claim 1, wherein the copper to be added is selectedfrom the group of copper compounds consisting of: cuprous oxide, cupricoxide, and the acefates, borate, carbonates, chlorides, cyanurate,hydroxides, nitrate, oxalate, phosphates, and sulfates, of copper.

4. The process of claim 1, wherein the tin to be added is selected fromthe group consisting of: metallic tin, stannic oxide, stannous oxide,and the chlorides, oxalate, and sulphates, of tin.

5. The process of claim 1, wherein the copper to be added is selectedfrom the group consisting of: cuprous oxide, cupric oxide, and the"acetates, borate, carbonates, chlorides, cyanurate, hydroxides,nitrate, oxalate, phosphates, and sulfates, of copper.

6. The process of claim 1, wherein the glass-making batch includes ametallic compound selected from'the .group consisting of the acetate,borate, chloride, hydroxide,.nitrate, nitrite, oxalate, peroxide,phosphates, silicate, sulfate, carbonate, oxide and sulfite of barium;and the acetate, bob-ate, carbonate, chloride, hydroxide, nitrate,nitrite, oxalate, oxide, peroxide, phosphates, silicate, sulfate, andsulfite, or strontium; in such quantity that the concentration of bariumand strontium in the finished glass, in terms of barium oxide andstrontium oxide, falls between 0.1% and 1.0%. a

References Cited in the file of this patent UNITED STATES PATENTS2,174,554 Dobrovolny et a1 Oct. 3, 1939 A a n.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pzstent N0. 2 922720 January 26 19 0 Thomas B, Parks It is hereby certified that errorappears in the printed specification of the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 6,, line 33 for extension read extensive line 68 for "moleculesor": read molecules of Signed and sealed this 9th day of August 1960.,

(SEAL) Attest:

KARL AXLINE ROBERT c. WATSON Attesting Oflicer Commissioner of Patents

1. A PROCESS FOR DIRECTLY FORMING A RUBY RED GLASS HAVING COLOR DEPENDENT UPON THE PRESENCE OF COPPER, INCLUDING THE STEPS OF ADDING TO A SILICATE-GLASS-MAKING BATCH A COMPLEX COMPRISING A COPPER-TIN-BIURET INCLUDING A COMPONENTS A COPPER COMPOUND, A TIN COMPOUND AND UREA IN AN APPROXIMATE PROPORTION RANGING FROM 4 TO 10 MOLECULES OR UREA FOR EACH ATOMIC WEIGHT OF CUPROUS COPPER, SAID BIURET BEING IN QUANTITIES AND PROPORTIONS SUFFICIENT TO CAUSE THE CONCENTRATION OF COPPER IN THE FINISHED GLASS, IN TERMS OF COPPER OXIDE, TO FALL BETWEEN 0.03% AND 0.25%, AND THE CONCENTRATION OF TIN, IN TERMS OF STANNIC OXIDE, TO FALL BETWEEN 1/4 AND 31/2 TIMES THE CONCENTRATE OF COPPER, AND THEN FUSING AND FINING SAID BATCH IN AN OPEN FURNACE. 